A sewage treatment material with synergistic photothermal evaporation and photocatalysis and its preparation method

Abstract

The present invention provides a sewage treatment material that combines photothermal evaporation and photocatalysis. The sewage treatment material is delignified wood, which includes an upper photothermal layer and a lower photocatalytic layer. The upper photothermal layer is a carbonized layer obtained by surface carbonization treatment, and the lower photocatalytic layer is loaded with a photocatalytic degradation material. Through the synergistic effect between the photothermal layer and the photocatalytic layer, the efficiency of photothermal water evaporation and photocatalysis is greatly improved. While degrading organic pollutants to meet the wastewater discharge standard, clean distilled water can be obtained, the wastewater discharge can be reduced, the concentration recovery and reuse of valuable components in the wastewater can be realized, the treatment cost of printing and dyeing wastewater can be effectively reduced, and the wastewater treatment efficiency can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and more specifically, relates to a sewage treatment material with synergistic photocatalytic evaporation and its preparation method. Background Art

[0002] Water resources are the most important natural resources for human beings. With the development of human society, more and more countries and regions will face the problem of freshwater shortage. Industrial production activities not only consume a large amount of water, but also generate industrial wastewater containing organic pollutants, which not only exacerbates the shortage of water resources, but also brings serious pollution, threatening the ecological environment safety and human health. Among them, the wastewater discharged from the printing and dyeing industry often contains high concentrations of organic pollutants, has high chroma, complex composition, and poor biodegradability, making the adsorption method and biological method in traditional wastewater treatment not ideal for printing and dyeing wastewater treatment. With the tightening of national environmental protection policies, new and more stringent requirements have been put forward for the quality and quantity of wastewater discharge, further increasing the difficulty of wastewater treatment.

[0003] As an environmentally friendly and low-energy-consuming sustainable wastewater treatment technology, photocatalytic oxidation technology has high catalytic oxidation activity and can efficiently degrade organic pollutants in water without selectivity. Therefore, it has good application prospects in the field of printing and dyeing wastewater treatment. However, other components in the wastewater, such as oil agents, acids, alkalis, inorganic salts, and heavy metal ions, are difficult to be removed by catalytic degradation and will still remain in large amounts in the wastewater after photocatalysis. At the same time, problems such as the high cost and difficult recycling of photocatalysts also affect the application of photocatalytic degradation technology in wastewater treatment.

[0004] As an emerging clean water resource acquisition technology, photothermal evaporation technology can utilize the photothermal conversion of solar energy to achieve interfacial evaporation, thereby obtaining clean distilled water, which has potential application prospects in the field of wastewater treatment. Applying the synergistic effect of photocatalytic degradation and photothermal evaporation to wastewater treatment can not only degrade pollutants, reduce environmental pollution, but also obtain clean water resources, reduce the wastewater discharge, and effectively realize the recycling and utilization of printing and dyeing wastewater.

[0005] At present, there are few reports on the combination of the two methods. Most of them utilize the photothermal conversion characteristics of materials to enhance the photocatalytic performance. For example, Fan et al. assembled Ag-AgCl / WO3 / g-C3N4 nanoparticles onto dopamine-modified melamine sponges through layer-by-layer self-assembly, combining the photothermal conversion effect of dopamine and the photocatalytic activity of nanoparticles to achieve efficient degradation of trimethoprim in sewage (ACS Appl. Mater. Interfaces, 2021, 13, 31066-31076). However, the above method only improves the degradation efficiency of sewage and does not achieve the synergistic effect of photocatalytic degradation and photothermal water evaporation, and cannot effectively achieve the goals of efficient water treatment and wastewater reduction. Summary of the Invention

[0006] Aiming at the above existing technical problems, the primary object of the present invention is to provide a sewage treatment material with synergistic photothermal evaporation and photocatalysis, including a photothermal layer and a photocatalytic layer. Through the synergistic effect between the photothermal layer and the photocatalytic layer, the photothermal water evaporation efficiency and photocatalytic efficiency are greatly improved. While degrading organic pollutants to make the wastewater meet the discharge standard, clean distilled water can also be obtained, reducing the wastewater discharge, realizing the concentration recovery and reuse of valuable components in the wastewater, effectively reducing the treatment cost of printing and dyeing wastewater, and improving the efficiency of wastewater treatment.

[0007] The second object of the present invention is to provide a preparation method of a sewage treatment material with synergistic photothermal evaporation and photocatalysis.

[0008] The third object of the present invention is to provide the application of the above sewage treatment material with synergistic photothermal evaporation and photocatalysis in photocatalytic degradation and / or photothermal water evaporation.

[0009] To achieve the above objects, the present invention is realized through the following technical solutions:

[0010] A sewage treatment material with synergistic photothermal evaporation and photocatalysis, the sewage treatment material is delignified wood, including an upper photothermal layer and a lower photocatalytic layer. The upper photothermal layer is a carbonized layer obtained by surface carbonization treatment, and the lower photocatalytic layer is loaded with a photocatalytic degradation material.

[0011] The present invention provides a sewage treatment material that combines photothermal evaporation and photocatalysis. Natural wood is used as a carrier after delignification modification, and the surface layer is carbonized to serve as a photothermal layer; the lower layer is loaded with a photocatalytic degradation material to serve as a photocatalytic layer, constructing a double-layer photothermal-photocatalytic coupled sewage treatment device. There is an excellent synergistic effect between the photothermal layer and the photocatalytic layer, greatly improving the photothermal water evaporation efficiency and the photocatalytic degradation efficiency. More specifically, the lower photocatalytic layer can effectively increase the water evaporation rate of the upper photothermal layer: the double-layer structure provided by the present invention has the Janus property of being hydrophobic on the upper layer and hydrophilic on the lower layer. During the interfacial solar water evaporation process, the hydrophilic wood pores in the lower layer can continuously transport water to the evaporation interface, improving the photothermal water evaporation efficiency. The upper photothermal layer can effectively increase the photocatalytic degradation rate of the lower photocatalytic layer: the presence of the upper photothermal layer can not only increase the local temperature, thereby enhancing the photocatalytic activity and accelerating the reaction rate; in addition, since the evaporation process drives the solution to flow upward, pollutants are concentrated at the bottom of the device, further increasing the catalytic efficiency. While the present invention degrades organic pollutants to meet the wastewater discharge standard, it can also obtain clean distilled water, reduce the wastewater discharge volume, realize the concentration recovery and reuse of valuable components in the wastewater, effectively reduce the treatment cost of printing and dyeing wastewater, and improve the efficiency of wastewater treatment.

[0012] Preferably, the thickness ratio of the carbonized layer is 10 - 50%. The thickness of the upper carbonized layer has a certain influence on both the photothermal water evaporation efficiency and the photocatalytic efficiency. In the present invention, wood with a thickness of 5 - 10 mm is usually selected. When the thickness of the wood is 5 mm, the thickness ratio of the carbonized layer is 0.5 - 2.5 mm; when the thickness of the wood is 10 mm, the thickness ratio of the carbonized layer is 1 - 5 mm.

[0013] Preferably, the loading amount of the photocatalytic degradation material is 5 - 13.5 wt%. Specifically, the loading amount is the mass ratio of the photocatalytic degradation material to the wood.

[0014] Further preferably, the thickness ratio of the carbonized layer is 10 - 40%; the loading amount of the photocatalytic degradation material is 10 - 13.5 wt%. Within this preferred range, the water evaporation rate of the upper photothermal layer is higher than 1.7 kg / (m 2 ·h); the photocatalytic degradation efficiency of the lower photocatalytic layer is higher than 98%.

[0015] Preferably, the photocatalytic degradation material is FeOOH nanoparticles.

[0016] Further preferably, the FeOOH nanoparticles are β-FeOOH nanoparticles.

[0017] In addition, the present invention also protects a method for preparing a sewage treatment material with the synergism of photothermal evaporation and photocatalysis, comprising the following steps:

[0018] S1. The delignified wood is carbonized to form delignified wood with a carbonized layer on the upper layer;

[0019] S2. The delignified wood with the carbonized layer on the upper layer is placed in an iron salt solution with the carbonized layer facing upward. The pH of the iron salt solution is adjusted to be acidic, and it is heated in a water bath at 40 - 90 °C, so that the hydrolyzed FeOOH nanoparticles are loaded in the pores of the non-carbonized lower-layer wood. Then it is washed and dried to obtain the sewage treatment material with the synergism of photothermal evaporation and photocatalysis.

[0020] Preferably, in step S1, the carbonization treatment is: the delignified wood is heated at 250 - 550 °C for 8 - 45 s.

[0021] More preferably, in step S1, the carbonization treatment is: the delignified wood is heated at 250 - 550 °C for 15 - 30 s.

[0022] Preferably, in step S2, the iron salt solution is a ferric chloride solution, and the concentration of the ferric chloride solution is 0.01 mol / L.

[0023] Preferably, after the delignified wood is placed in the iron salt solution in step S2, the time for the iron salt solution to enter the wood pores can be reduced by means of vacuum pumping.

[0024] More preferably, the time of vacuum pumping ≥ 1 h.

[0025] Preferably, in step S2, the time of water bath heating is 6 - 96 h.

[0026] More preferably, in step S2, the time of water bath heating is 12 - 96 h.

[0027] Specifically, the method for preparing the delignified wood is: the wood is soaked in a bleaching solution to remove lignin and hemicellulose, then washed and freeze-dried to obtain the delignified wood.

[0028] Preferably, the bleaching solution is a sodium hypochlorite solution with a mass concentration of 4 - 10%.

[0029] Preferably, the soaking time is 5 - 10 h.

[0030] Preferably, the cleaning is performed by rinsing with ultrapure water, such that the change in the solution conductivity is less than 4 μs / cm. The cleaning is to remove unreacted sodium hypochlorite. After rinsing, the sodium hypochlorite adsorbed on the wood surface dissociates into the water, so there is a certain conductivity in the solution. If the solution conductivity is lower than this range, it indicates that the sodium hypochlorite on the wood surface has been basically removed.

[0031] Furthermore, the application of the above-mentioned sewage treatment material with synergistic photothermal evaporation and photocatalysis in photocatalytic degradation and / or photothermal water evaporation should also be within the protection scope of the present invention.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The present invention constructs a double-layer photothermal-photocatalytic coupled sewage treatment device, which has excellent synergistic effects between the photothermal layer and the photocatalytic layer, greatly improving the photothermal water evaporation efficiency and the photocatalytic degradation efficiency. The double-layer structure provided by the present invention has the Janus property of being hydrophobic on the upper layer and hydrophilic on the lower layer. During the interfacial solar water evaporation process, the hydrophilic wood pores on the lower layer can continuously transport water to the evaporation interface, improving the photothermal water evaporation efficiency. In addition, the presence of the upper photothermal layer can not only increase the local temperature, thereby enhancing the photocatalytic activity and accelerating the reaction rate; moreover, due to the upward flow of the solution driven during the evaporation process, pollutants are enriched at the bottom of the device, further increasing the catalytic efficiency.

[0034] (2) By optimizing the carbonization treatment, hydrolysis reaction and other process steps and conditions of the sewage treatment material with synergistic photothermal evaporation and photocatalysis of the present invention, the water evaporation rate of the sewage treatment wood with synergistic photothermal evaporation and photocatalysis prepared is greater than 1.7 kg / (m 2 ·h), and the photocatalytic degradation efficiency of the lower photocatalytic layer is higher than 98%. The degradation rates of 50 mL of dye solutions with a concentration of 50 mg / L such as methylene blue, methyl orange, and Sudan red B all reach 95-100% within 30 minutes.

[0035] (3) The wastewater treated by the present invention can be divided into two parts. One part is the pure distilled water collected by interfacial evaporation using sunlight, and the other part is the wastewater that can be discharged after removing organic pollutants. At the same time, the wastewater discharge amount is greatly reduced compared with the traditional method. Description of the Drawings

[0036] Figure 1 It is a schematic diagram of the structure and application of the sewage treatment material with synergistic photothermal evaporation and photocatalysis.

[0037] Figure 2 It is the XRD pattern of the photocatalytic layer in the sewage treatment material with synergistic photothermal evaporation and photocatalysis.

[0038] Figure 3It is a scanning electron microscope image of the photocatalytic layer in the material for synergistic sewage treatment by photothermal evaporation and photocatalysis.

[0039] Figure 4 It is the dynamic contact angle of the carbonized layer and the photocatalytic layer in the material for synergistic sewage treatment by photothermal evaporation and photocatalysis. Specific embodiments

[0040] The present invention will be further described below in conjunction with the specification drawings and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0041] Example 1

[0042] A preparation method of a material for synergistic sewage treatment by photothermal evaporation and photocatalysis includes the following steps:

[0043] (1) Immerse balsa wood chips with a size of 30mm×30mm×5mm in a sodium hypochlorite solution with a mass concentration of 4-10%, react at room temperature for 5h, then rinse with ultrapure water until the change in solution conductivity is lower than 4 μs / cm, and freeze-dry to obtain delignified wood.

[0044] (2) Place the delignified wood obtained in step (1) flat on a hot stage at 550°C, and perform carbonization treatment on the wood surface for about 15s to form a carbonized layer with a thickness of about 1mm on the wood surface.

[0045] (3) Prepare a 0.05mol / L ferric chloride solution, place the carbonized wood obtained in step (2) with the carbonized layer facing up and floating naturally on the surface of the ferric chloride solution, evacuate for 1h to accelerate the entry of the ferric chloride solution into the pores of the lower-layer wood, add a 0.01mol / L hydrochloric acid solution to the solution, and place it in a water bath at 60°C for hydrolysis for 24h, so that the hydrolyzed β-FeOOH nanoparticles are loaded into the pores of the lower-layer uncarbonized wood. The loading amount of FeOOH nanoparticles is 10.27wt%. After washing and drying, a material for synergistic sewage treatment by photothermal evaporation and photocatalysis with an upper photothermal layer (carbonized layer) - lower photocatalytic layer (loaded with FeOOH nanoparticles) is obtained.

[0046] Example 2

[0047] The difference between this example and Example 1 is that in step (2), the carbonization time is 30s, and a carbonized layer with a thickness of about 2mm is formed on the wood surface.

[0048] Example 3

[0049] The difference between this example and Example 1 is that in step (2), the carbonization time is 45s, and a carbonized layer with a thickness of about 2.5mm is formed on the wood surface.

[0050] Example 4

[0051] The difference between this example and Example 1 is that: in step (3), the hydrolysis time is 6 h, and the loading amount of FeOOH nanoparticles is 3.99 wt%.

[0052] Example 5

[0053] The difference between this example and Example 1 is that: in step (3), the hydrolysis time is 12 h, and the loading amount of FeOOH nanoparticles is 8.52 wt%.

[0054] Example 6

[0055] The difference between this example and Example 1 is that: in step (3), the hydrolysis time is 48 h, and the loading amount of FeOOH nanoparticles is 11.94 wt%.

[0056] Example 7

[0057] The difference between this example and Example 1 is that: in step (3), the hydrolysis time is 72 h, and the loading amount of FeOOH nanoparticles is 12.94 wt%.

[0058] Example 8

[0059] The difference between this example and Example 1 is that: in step (2), the carbonization time is about 8 s, and a carbonized layer about 0.5 mm thick is formed on the wood surface; in step (3), it is hydrolyzed in a water bath at 90 °C.

[0060] Example 9

[0061] The difference between this example and Example 1 is that: in step (3), it is hydrolyzed in a water bath at 40 °C for 96 h, and the loading amount of FeOOH nanoparticles is 13.5 wt%.

[0062] Comparative Example 1

[0063] The difference between Comparative Example 1 and Example 1 is that: only step (1) is carried out, and steps (2) and (3) are not carried out to obtain delignified wood.

[0064] Comparative Example 2

[0065] The difference between Comparative Example 2 and Example 1 is that: only steps (1) and (2) are carried out, and step (3) is not carried out to obtain carbonized wood.

[0066] Comparative Example 3

[0067] The difference between Comparative Example 3 and Example 1 is that: step (1) treatment is not carried out, and the balsa wood chips are directly subjected to step (2) treatment, and the loading amount of FeOOH nanoparticles is 3.24 wt%.

[0068] Comparative Example 4

[0069] The difference between Comparative Example 4 and Example 1 is that: without performing the treatment of step (2), the delignified wood obtained in step (1) is directly subjected to the treatment of step (3), and the loading amount of FeOOH nanoparticles is 12.83 wt%.

[0070] In the above examples and comparative examples, the test method for the loading amount of FeOOH in the photocatalytic layer is as follows: the wood loaded with FeOOH nanoparticles is subjected to thermogravimetric test. At high temperature, hemicellulose and cellulose in the wood undergo thermal cracking, and the remaining residue is Fe2O3, the oxidized product of FeOOH, so as to infer the loading amount of FeOOH.

[0071] Test Example 1

[0072] The photocatalytic layer of the photo-thermal evaporation and photocatalysis synergistic sewage treatment material prepared in Example 1 was subjected to XRD detection and scanning electron microscopy detection.

[0073] Figure 1 is a schematic diagram of the structure and application of the material, Figure 2 is a diagram of the XRD detection result, Figure 3 is a cross-sectional scanning electron micrograph of the photocatalytic layer. It can be seen that after the wood is delignified, a large amount of cellulose is exposed on the surface, which can chelate with iron ions, so that the hydrolyzed β-FeOOH nanocrystals are successfully loaded into the pores of the non-carbonized layer wood.

[0074] At the same time, as a porous material, by comparing the dynamic contact angles of the surfaces of the photo-thermal layer and the photocatalytic layer of the double-layer device, the specific operation is as follows: use the OCA 15EC contact angle measuring instrument of Dataphysics company to observe the hydrophilic and hydrophobic properties of the upper and lower layers of the wood. Each time, 3 μL of water droplets are dropped, and its initial contact angle and dynamic contact angle (the contact angle at different times after the water droplet contacts the surface) are measured, and the immersion time of the liquid droplet into the wood is compared.

[0075] The results are as Figure 4 shown. By observing the time for the water droplet to penetrate from the surface of the contact material to completely immerse into the pores to compare the hydrophilic and hydrophobic differences between the materials, it is found that the water droplet penetrates from the surface of the carbonized photo-thermal layer to the other side after a long time, while spreads and disappears on the surface of the photocatalytic layer in a very short time, proving that the photo-thermal layer has hydrophobic properties, while the photocatalytic layer has hydrophilic properties, and the device as a whole has a Janus structure.

[0076] Test Example 2

[0077] The photo-thermal evaporation and photocatalysis synergistic sewage treatment materials prepared in the above examples and comparative examples were subjected to photo-thermal water evaporation test and photocatalytic degradation test. The photo-thermal water evaporation test was carried out at 1 kW / m 2It was carried out under a xenon lamp. In the photocatalytic degradation test, the dye wastewater was methylene blue solution. After preparing 50 mL of 20 mg / L methylene blue solution, the pH was adjusted to 3 and 20 μL of hydrogen peroxide was added as the raw material solution. Under a xenon lamp with a power of 1 kW / m 2 reacted for 30 min, and the changes in ultraviolet-visible light absorbance before and after the reaction were measured to compare the dye concentration after the reaction. The data of the photothermal water evaporation rate and photocatalytic degradation efficiency of the photothermal evaporation and photocatalytic synergistic sewage treatment materials prepared in each example and comparative example are shown in Table 1 below.

[0078] Table 1

[0079]

[0080]

[0081] As can be seen from Examples 1 to 3 above, as the carbonization time increases, the thickness of the wood carbonization layer increases, but the photothermal water evaporation rate of the material changes little. However, due to the corresponding decrease in the thickness of the photocatalytic layer, the photocatalytic degradation efficiency decreases slightly.

[0082] As can be seen from Examples 1 and 4 to 7 above, as the hydrolysis time of the ferric chloride solution increases, the loading amount of FeOOH nanoparticles in the photocatalytic layer of the material increases, and the photothermal water evaporation performance is basically not affected. After the hydrolysis time exceeds 12 h, the photocatalytic degradation performance reaches stability. The photothermal water evaporation rate and photothermal degradation efficiency of the sewage treatment materials prepared in Examples 8 and 9 are equivalent to those in Example 1.

[0083] As can be seen from Comparative Example 1 and Example 1, in Comparative Example 1, the wood was not carbonized and did not carry FeOOH nanoparticles, and its photothermal water evaporation rate was 0.67 kg / (m 2 ·h), and the photocatalytic degradation efficiency was 23.6%, both of which were much lower than those in Example 1. The wood without FeOOH nanoparticles loaded in Comparative Example 1 had a certain degradation efficiency. This is because the photocatalytic degradation efficiency is calculated based on the solution concentration before and after the reaction. Since the wood has a certain adsorption effect, the solution concentration decreases after treatment; and the hydrophilicity of the wood can promote the interfacial water transfer, so there is a certain water evaporation rate.

[0084] As can be seen from Comparative Example 2 and Example 1, compared with Comparative Example 2, a lower photocatalytic layer loaded with FeOOH nanoparticles was formed in Example 1. The photocatalytic degradation efficiency of the material in Example 1 was greatly improved, and the photothermal water evaporation rate of the upper carbonization layer also increased to a certain extent. This shows that there is a synergistic effect between the lower photocatalytic layer and the upper carbonization layer.

[0085] As can be seen from Comparative Example 3 and Example 1, compared with Comparative Example 3, the wood in Example 1 was subjected to delignification treatment. It can be clearly seen that in Example 1 with delignification treatment, the loading amount of FeOOH nanoparticles loaded on the material was greatly increased, thereby improving the photocatalytic degradation efficiency of the material. This shows that after the wood is delignified, a large amount of cellulose is exposed on the surface and can chelate with iron ions, so that the FeOOH nanoparticles generated by hydrolysis are successfully loaded into the pores of the non-carbonized wood. In addition, the removal of lignin is also beneficial to the improvement of the photothermal water evaporation efficiency. Comparing Comparative Example 3 and Example 4, the thickness of the carbonized layer is the same and the loading amount of FeOOH nanoparticles is similar, but the photothermal water evaporation rate and photocatalytic degradation efficiency of Example 4 are much better than those of Comparative Example 3. The reason is that the hydrophilicity of the wood is greatly improved after delignification, providing a water transmission path, which is more conducive to the timely replenishment of water at the bottom of the wood to the evaporation interface, so the photothermal water evaporation effect is greatly improved; similarly, the water evaporation process also drives the upward transmission of the polluted substrate in the solution, making the dye molecules contact with the FeOOH nanoparticles more fully, thereby improving the degradation efficiency. This further reflects the synergistic effect of the present invention. As can be seen from Comparative Example 4 and Example 1, compared with Comparative Example 4, the wood in Example 1 was carbonized, and the water evaporation rate of the material was greatly increased; in addition, the carbonization treatment also affected the photocatalytic degradation efficiency of the material to a certain extent.

[0086] The foregoing examples are illustrative only and are used to explain some of the features of the method of the present invention. The appended claims are intended to claim as broad a scope as can be conceived, and the examples presented herein are demonstrated by the applicant's actual test results. Therefore, the applicant's intention is that the appended claims are not limited by the selection of examples that illustrate the features of the present invention. Some of the numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. A sewage treatment material that combines photothermal evaporation and photocatalysis, characterized in that The sewage treatment material is delignified wood, which includes an upper photothermal layer and a lower photocatalytic layer. The upper photothermal layer is a carbonized layer obtained by surface carbonization treatment, and the lower photocatalytic layer is loaded with a photocatalytic degradation material; The thickness ratio of the carbonized layer is 10-40%; the loading amount of the photocatalytic degradation material is 10-13.5 wt%; The photocatalytic degradation material is FeOOH nanoparticles.

2. The preparation method of the sewage treatment material with the synergism of photothermal evaporation and photocatalysis according to claim 1, characterized in that It includes the following steps: S1. The delignified wood is subjected to carbonization treatment to form delignified wood with a carbonized layer on the upper layer; S2. The delignified wood with the upper layer being the carbonized layer is placed in an iron salt solution with the carbonized layer facing upwards. The pH of the iron salt solution is adjusted to be acidic, and it is heated in a water bath at 40-90 °C, so that the hydrolyzed FeOOH nanoparticles are loaded in the pores of the lower layer of wood that has not been carbonized. After washing and drying, the sewage treatment material with synergistic photothermal evaporation and photocatalysis is obtained.

3. The preparation method according to claim 2, characterized in that, In the step S1, the carbonization treatment is: the delignified wood is heated at 250-550 °C for 8-45 s.

4. The preparation method according to claim 3, wherein The delignified wood is heated at 250-550 °C for 15-30 s.

5. The preparation method according to claim 2 or 3, characterized in that, In the step S2, the time of the water bath heating is 6-96 h.

6. The preparation method according to claim 5, characterized in that, The time of the water bath heating is 12-96 h.

7. The preparation method according to claim 2, wherein In the step S2, the iron salt solution is a ferric chloride solution.

8. Application of the sewage treatment material with synergistic photothermal evaporation and photocatalysis according to claim 1 or the sewage treatment material with synergistic photothermal evaporation and photocatalysis prepared by the preparation method according to any one of claims 2-7 in photocatalytic degradation and / or photothermal water evaporation.

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